Charles a



(No Model.)

0. A. ROLFE.

TELEGRAPH AND TELEPHONE SYSTEM. No. 534,970. Patented Feb. 26, 1895'.

Elm C'WulenserM 41:1: 7 g J enser- NITED STATES PATENT Erin.

CHARLES A. ROLFE, OF CHICAGO, ILLINOIS, ASSIGN OR TO THE POLICE TELEPHONE AND SIGNAL COMPANY, OF SAME PLACE.

TELEGRAPH AN 0 TELEPH ON E SYSTEM.

SIECIFICATION forming part of Letters Patent No. 534,970, dated February 26, 1895.

Application filed February 15, 1893. Serial No. 462,357. (No model.

To all whom it may concern.-

Be it known that 1, CHARLES A. ROLFE, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Telegraph and Telephone Systems, of which the following is a specification.

My invention relates to telegraph and telephone systems and is particularly serviceable in police signal telegraph and telephone systerns comprising a main signal line or circuit over which the usual calls or signals are transmitted and a neutral line normally open at both ends and arranged parallel to the main signal line, so that by placing a telephone employed at the main or central office, in connection with both the neutral line and the main line, the two can be used to establish-a circuit between the central office telephone and a telephone at the street or sub-station. In thus employing a neutral line as a means for avoiding disturbances while talking over a circuit involving both lines, the effectiveness of the neutral line is not uniform, and will be found to vary with different days. I have also found by practical experiment that on some days I can secure the best results by connecting up one end of the neutral line with the main line and main or central office telephone, while on other days like results can only be secured by connecting up the main line and central office telephone with the opposite end of the neutral line. To such end therefore, I provide in such system a switch suitable for connecting up the main line and telephone with one and the other of the normally open ends of the neutral line, alternately and at will, in which Way, I may at one time connect the telephone with the right of the neutral line and right of the main line, and at another time connect the telephone with the left of the neutral line and the left of the main line.

In the accompanying drawings Figure 1 is a diagrammatic representation of a system involving my invention. Fig. 2 illustrates one of the switch-levers.

The signal system comprises a receiving apparatus or instrument A. arranged at the main or central office, a street or other transmitting station box B. understood to comprise or conably this arrangement also includes a 0011- denser E. for purposes well known to those familiar with the art. street or transmitting station also comprises a telephone represented by the transmitter F, receiver F and hook F for the receiver, and

In like manner the preferably a condenser G. likewise provided for well known purposes. 7

The main signal line or circuit 1 is paralleled by an auxiliary or neutral line 2 having normally open ends and employed to neutralize effects resulting from induction which tend to create disturbance during the transmission of voice currents between the stations. As a matter of convenience, a three point switch H. is provided at the street station and arranged to connect the telephone thereat, with the main line 1 at either side of the signal transmitting instrument, it being observed that such connection is made through the switch when the receiver is off the hook. The street station telephone also connects with the neutral wire, and Where the condenser G. or analogous device is employed, the same can be placed in the branch between the telephone and the neutral Wire, as illustrated.

The ends of the neutral line or wire are normally open, and can be alternately connected up with the main signal line, and main or central office telephone, by means of a loop switch D. arranged at the main or central office.

V The loop switch D. comprises a pair of switch or contact levers D and D one of which is employed to connect the main or central office telephone with the right of the neutral line and right of the main line, while on the other hand, the remaining switch-lever is employed to connect the said telephone with the left of the neutral line and left of the main line. To such end therefore, the

telephone wire 3 is arranged to form a loop which includes a pair of contacts 4 allotted to the switch-lever D and a pair of contacts 5 allotted to the switch-lever D. The contacts 4 remain in electrical connection respectively with opposite sides of the switchlever D which latter is constructed with metallic sides 6 insulated from one another bya suitable insulating material as at 7, and likewise, the contacts 5 remain in electrical connection respectively with opposite sides of the switch-lever D which is constructed like the lever D The loop switch also comprises a couple ofcontacts 8 respectively allotted to the right of main line and right of neutral line, and a couple of like contacts 9 respectively allotted to the left of main line and left of neutral line. For such purpose, the endN. R. of the neutral right, connects with one of the contacts 8, while the right, M. R., the main signal line is connected with the remaining contact 8 by a branch 10. On the other hand the end N. L. of the neutral left, is connected with one of the contacts 9,while the left M. L. of the main signal line is connected with the remaining contact 9 by a branch 11.

The contacts 8 and 9 are arranged with relation to the switch-levers, and the latter are so constructed, that by bringing lever D between and in engagement with the contacts 8 the latter will connect with the telephone loop through the medium of the sides of said lever and its allotted contacts 5, while on the other hand, by bringing lever D between and in engagement with the contacts 9, said contacts will connect with the telephone loop through the sides of said leverZD and its allotted contacts L. The lever D can'therefore .be adjusted so as to place the main or central office telephone in connection with the normally open end of the right portion of the neutral line, and corresponding right portion of the main line, and conversely the lever D can be adjusted so as to place such telephone in connection with the normally open end of the left portion of the neutral line and corresponding left portion of the main line.

When the switch lever D is adjusted so as to bring its metallic sides in contact with the contact points 8, 8, the main or central office telephone, will as aforesaid, be in connection with the right portion of the neutral line (2 N. R.) and branch 10 of the right portion of the main line 1. The circuit will then be as follows, to wit:through the telephone apparatus at the main station, the telephone circuit 3, contact points 4 and 5, the opposite metallic sides of lever D, the contact points 8, the right portion of the main line including branch 10, the right portion of the neutral line (N. R), the wires connecting the main and neutral lines with the telephone apparatus at the sub station, and also through said telephone apparatus. On the other hand, when lever'D is out of contact with contact points 8, and lever D is adjusted so as to bring its metallic sides in contact with the contact points 9, the circuit will be as follows, to wit:- through the telephonelapparatus at the main station, the telephone circuit 3, the contact points 4 and 9, the metallic sides of lever D the left portion of the main line including branch 11, the left portion of the neutral line (N. L), the wires connecting the main and neutral lines with the telephone apparatus at the sub station, and also through said telephone apparatus.

When the main or central office telephone is not in use, both ends of the neutral line are left open, and this can be done by throwing the switch levers out of connection with their respectively allotted contacts 8 and 9,it being observed that by way of illustrating the functions of the switch levers, I have in Fig. 1 shown one of the levers in position to establish connection between contacts 5 and 8, and represented the remaining lever in position to break connection between the contacts 4 and 9. The construction of switch levers herein provided is best shown in Fig. 2, which represents the switch-lever D it being understood. that both switch-levers are constructed alike.

In this application I have elected to cover the special construction of switch D, while in my application Serial No. 485,715, wherein several constructions of switches are shown (including the switch of this application) I have broadly or generically covered matters common to all of said applications, and specially claimed aconstruction of switch which differs in specific construction from the switch I) herein described.

What I claim as my invention is The combination of the main signal line having branches, the neutral line, the main or central oflice telephone, and a switch comprising contact points 4 and 5 arranged in pairs and connected up with said telephone, a couple of contact points 8 respectively connccted with the right of the neutral line and one branch of the main line, a couple of contacts 9 respectively connected with the left of the neutral line and the other branch of the main line, and levers D, D having conducting sides insulated one from the other, one of said levers being arranged for establishing connection between contact points 4 and 9, and the other being arranged for establishing connection between contact points 5 and 8, substantially as and for the purpose described.

CHARLES A. ROLFE.

Witnesses:

BETA M. WAGNER, W. D. MIDDLETON.

IIO 

